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Amount by which Company may increase the term length of the credit agreement.

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The debt-to adjusted capital ratio which the Company must not exceed in accordance with the terms of the line of credit facility agreement.

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Number of banks participating in revolving credit and letter of credit agreement

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Payments For Debt Tender And Redemption

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Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Face (par) amount of the original debt instrument that was repurchased.

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Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Debt - Narrative (Details)			3 Months Ended
Debt - Narrative (Details)	Apr. 15, 2020 USD ($)	Apr. 01, 2020 USD ($)	Mar. 31, 2020 USD ($) bank	Dec. 31, 2019 USD ($) bank	Mar. 31, 2019 USD ($)	Mar. 16, 2020 USD ($)
Debt Instrument [Line Items]
Net proceeds on issuance of long-term debt			$ 3,470,000,000		$ 0
Aggregate principal amount of outstanding debt securities under tender offer and optional redemption			3,200,000,000
Aggregate principal amount of outstanding debt securities under tender offer			1,450,000,000
Aggregate principal amount of outstanding debt securities under optional redemption			1,760,000,000
Loss on repurchase of debt, pre-tax			185,000,000		0
Loss on repurchase of debt, after-tax			140,000,000
Repayment of long-term debt			4,209,000,000		$ 1,000,000,000
Payments for debt tender and redemption			3,200,000,000
Commercial paper			$ 770,000,000	$ 944,000,000
Commercial Paper
Debt Instrument [Line Items]
Weighted average interest rate, commercial paper			2.28%
Subsequent Event
Debt Instrument [Line Items]
Aggregate principal amount of outstanding debt securities under tender offer and optional redemption	$ 289,000,000
Loss on repurchase of debt, pre-tax
Medco Notes
Debt Instrument [Line Items]
Aggregate principal amount			$ 349,000,000
Stated interest rate			4.125%
Revolving Credit Agreement
Debt Instrument [Line Items]
Number of participating banks \| bank			23
Maximum borrowing capacity			$ 3,250,000,000
Amount by which credit facilty amount can be increased			$ 500,000,000
Amount by which credit facilty term length can be increased			1 year
Leverage ratio covenant			60.00%
Revolving Credit Agreement \| Letter of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 500,000,000
364-day Revolving Credit Agreement \| Revolving Credit Facility
Debt Instrument [Line Items]
Number of participating banks \| bank				23
Maximum borrowing capacity				$ 1,000,000,000.0
Credit agreement term				364 days
364-Day Term Loan
Debt Instrument [Line Items]
Leverage ratio covenant			60.00%
364-Day Term Loan \| Subsequent Event \| Line of Credit
Debt Instrument [Line Items]
Credit agreement term		364 days
Aggregate principal amount		$ 1,400,000,000
Prepayment rate		20.00%
Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount						$ 3,500,000,000